I checked the source files and it appears the spatialite backend is not patched for this issue in this version, and is still using compilers etc. from django.contrib.gis.db.models.sql.compile instead of django.contrib.gis.db.models.spatialite.compile (which is missing)
merging the previous commits would solve it I guess...
I stand corrected, this seems to have moved down, outside the spatialite backend into the base sql backend, my appologies. I can correctly get the values as datatime objects in a shell.
The bug occurs when using the 'date_hierarchy' on an admin model, checking revealed the aggregate function still does not seem to call convert_values()